Protective cover for a ventilation opening

ABSTRACT

A protective cover is provided for a ventilation opening in a plant space of a nuclear-engineering plant. The cover is configured, with a construction that is simple, and with simple manufacture and mounting, for a sufficient air-flow cross section and also for protection against ingress of destructive projectiles into the building interior. The protective cover has profile elements, which are arranged in a mounting plane in a rectangular frame, are aligned in a longitudinal direction such that they are parallel to one another, and are shaped in the same way and orientated in the same way. The relevant profile element has an L-shaped or V-shaped cross section with two limbs that meet in a peak, with the peaks pointing in the transverse direction. A spacing between profile elements that immediately follow each other is chosen such that there is no rectilinear passage between them.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2011 111 666.8, filed Sep. 1, 2011; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a protective cover (in short: cover) for a ventilation opening in a plant space or plant building of a nuclear-engineering plant.

The plant spaces of a nuclear-engineering plant located outside the reactor containment include among others for example what is referred to as diesel generator building, which houses safety-relevant cooling systems and/or associated diesel generators. The walls of such plant spaces are provided with supply-air/exhaust-air openings (in short: ventilation openings), which are typically configured as solid prismatic reinforced-concrete ducts. The geometry and through-guidance of such ducts requires as a rule large planning outlay and high costs. Not only must the ventilation openings ensure a sufficient air-flow cross section for the unimpeded operation of the cooling unit. There should also be provided sufficient ingress protection with respect to what is referred to as tornado missiles and similar projectiles and high-energy fragments that are set free during, for example, a hurricane (tornado) in the vicinity of the relevant plant building. For this purpose, the relevant ventilation opening is typically provided with a cover in the manner of a steel grid. However, it has been found that the hitherto known covers meet the requirements that are expected of them only in part, such that there is a need for improvement in this regard.

SUMMARY OF THE INVENTION

The present invention is therefore based on the object of further developing a protective cover of the type mentioned in the introduction such that, with a construction that is kept simple, and with simple manufacture and mounting, the abovementioned requirements—sufficient air-flow area and simultaneously protection against ingress of destructive projectiles into the building interior—are met to a high degree.

This object is achieved according to the invention by the features of the claims.

Accordingly, a protective cover for a ventilation opening in a plant space of a nuclear-engineering plant is provided. The cover has a plurality of elongate profile elements, which are arranged in a mounting plane in a rectangular frame having a longitudinal direction and a transverse direction, are aligned in the longitudinal direction such that they are parallel to one another, and are shaped in the same way and orientated in the same way. The relevant profile element has an L-shaped or V-shaped cross section with at least two limbs that meet in a peak, with the peaks pointing in the transverse direction, and the spacing between profile elements that immediately follow each other is chosen such that there is no rectilinear passage between them.

As will be described in more detail further below, this realizes a penetration protection against airborne projectiles coming from any directions while having a high mechanical load capacity.

In a preferred embodiment, the two limbs of the relevant profile element meet in the peak at an angle that ranges from 80° to 110° and is preferably 90° (right angle). The advantage over other angle ranges and over rounded embodiments, for example arc-shaped or wave-shaped profile elements, is that primarily effective perforation protection is achieved with comparatively simple and economic measures, coupled with a high load-bearing capacity on impact of impact bodies.

It is furthermore advantageous if, when viewed in the transverse direction, the spacing which characterizes the overlap between the leading edge of a profile element and the trailing edge of the profile element that is located immediately in front of it is approximately 0.5% to 5% of the total width of the relevant profile element in the transverse direction.

A symmetrical embodiment, in which the two limbs of the relevant profile element have the same dimensions, is particularly expedient.

It is particularly expedient and advantageous from a production-technological viewpoint if the cross section of the relevant profile element is constant over its entire longitudinal extent.

The relevant profile element advantageously has two end faces, at which it is welded to the frame.

In a configuration that is particularly advantageous for reasons of economic efficiency, strength and stability, the relevant profile element is configured in a unipartite manner and produced by bending an originally planar steel sheet. The profile element could, however, for example also be cast in one piece in the desired contour, that is to say as an L profile. Alternatively, two elongate, flat and preferably rectangular steel-sheet strips can also be connected to each other, in particular welded, to form the profile element. Particularly preferred is in any case the use of catalogued standard steel profiles.

The frame is for its part advantageously composed of profile elements with U-shaped or double-U-shaped (two U profiles that meet at their base sides) cross sections.

All the profile elements are expediently produced from steel and are welded to one another at the connection locations.

The dimensions of the individual components and the connections between them are preferably chosen such that the cover is also configured for both comparatively high static surface loads and for concentrated dynamic impact loads.

The easy-to-mount/dismantle cover, prefabricated in modular units, in the manner of a regular steel protective grid or steel grid serves as a passive protection apparatus for safety-relevant components in nuclear plants. The cover is directly arranged on, adjusted and subsequently attached to the outer shell of a building over an existing cutout/mounting opening. When required, for example for repair works or to exchange defective components inside the building, the protective grid can be dismantled and removed.

The grid structure is configured and dimensioned in a manner such that it ensures a sufficient air-flow cross section for unimpeded operation of the cooling unit while being active as a full protective barrier in order to protect the safety-relevant cooling system installed in the building structure against potential intruding hard and also deformable projectiles, which can occur for example during a tornado. The proper functioning of the specially configured steel gridwork system was mathematically proven. It satisfies all defined criteria/requirements that must be taken into account when configuring protective barriers against impacting standard projectiles as are defined, for example, in the Regulatory Guide 1.76 by the U.S. Nuclear Regulatory Commission (NRC) for the protection against tornado missiles. The protective barrier accordingly protects against penetration and perforation.

Counted among the advantages of the construction are also the simple pre-fabrication in the workshop, the short installation time on the construction site and the simple dismantlability of the steel construction in the event of repair works or component exchange.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a protective cover for a ventilation opening, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, plan view of a protective cover for a ventilation opening according to the invention;

FIG. 2 is a perspective, detail view of the cover according to FIG. 1;

FIG. 3 is a cross sectional view through the cover according to FIG. 1 and taken along the section line III-III of FIG. 1, together with a few surrounding building components to which the cover is attached;

FIG. 4 is an illustration of detail A from FIG. 3; and

FIG. 5 is a perspective view of a part of a plant space of a nuclear-engineering plant with two ventilation openings in the ceiling that are secured in each case by the cover according to FIG. 1.

DESCRIPTION OF THE INVENTION

Identical parts or parts with identical action are provided with the same reference symbols in all figures.

The protective cover (in short: cover) 2 illustrated in FIGS. 1 to 3 serves as a passive protection apparatus for a ventilation opening 4 in a plant space 6 of a nuclear-engineering plant, in particular a nuclear power plant. It contains a frame 10 that is formed by four profile elements 8 composed of steel with in each case a U-shaped cross section. Limbs 12 of the profile elements 8 point—as can be seen clearly in FIG. 3—in each case to the outside. Mutually abutting profile elements 8 are welded together in corners 14, which are cut for a miter joint. The frame 10 has the shape of a rectangle with a longitudinal side 16 and a transverse side 18. The terms longitudinal side and transverse side are used here merely to uniquely identify the directions and possess no implication whatsoever with respect to the relative lengths. That is to say that the transverse side 18 can, in a deviation from the illustration in FIG. 1, potentially also be longer than the longitudinal side 16. A longitudinal direction 20 and a transverse direction 22 are defined accordingly. The frame 10 is subdivided into a plurality of subframes—five pieces in FIG. 1—using a number of profile elements 24 made of steel, which are aligned in the transverse direction 22 and have in each case a double-U-shaped cross section. The limbs of the profile elements 24 point in this case to the outside in the direction of the transverse-side profile elements 8 of the outer frame 10. At the end faces, the profile elements 24 are welded together with the longitudinal-side profile elements 8 of the outer frame 10. It is also possible not to subdivide the frame 10 into subframes if the longitudinal sides 16 are sufficiently short.

As can be seen in FIG. 3, the frame 10 of the cover 2, after it has been mounted, lies on the edge or the mounting surround of a corresponding ventilation opening 4 in a building wall 26, in particular a ceiling wall. This refers in the present case to a building's exterior ceiling, but could also be a building's exterior wall or an inner wall or inner ceiling with comparable requirements. The cover 2 is fixed, in particular screwed using thread bolts 30, to the building wall (here: building ceiling) 26 via an outwardly directed extension arm 28 that is welded to the profile elements 8 of the outer frame 10. To this end, the building wall 26 can be provided with corresponding anchor plates or the like.

Arranged inside the relevant frame 10 or subframe are a plurality of elongate profile elements 32 made of steel, which are aligned in the longitudinal direction 20 such that they are parallel to one another, and are shaped in the same way and orientated in the same way, with the profile elements 32 being welded at their end faces to the transverse-side U-shaped profile elements 8 or to the double-U-shaped profile elements 24. The relevant profile element 32 has in the exemplary embodiment an L-shaped cross section which is constant over the entire longitudinal extent, with two straight limbs 36 of identical limb length, which meet in a peak 34 at a right angle) (α=90), as can be seen most clearly in FIG. 3 or FIG. 4. The relevant profile element 32 is formed from a catalogued right-angled steel profile or is formed from two welded-together metal-sheet strips. Alternatively, the profile element 32 is formed from an originally rectangular, planar steel sheet that was bent at a right angle along its central longitudinal line such that, viewed in the cross section, the peak 34—or, viewed over its entire longitudinal extent, the corresponding leading edge—is formed. The peaks 34 of all the profile elements 32 are arranged on a common imaginary straight line and point in the same direction, in this case in the transverse direction 22 toward one of the longitudinal-side profile elements (hollow profiles) 8 of the frame 10.

The spacing a—viewed in the transverse direction 22—between the profile elements 32 that immediately follow each other is selected to be the same size for all the profile elements 32 of a subframe or frame 10, specifically in a manner such that there is no rectilinear passage between them. This means, according to the detail view in FIG. 4, that the profile elements 32 are attached to the profile elements 8 or 24 of the frame or subframe in a manner such that they are stacked or nested one within another. The overlap between two adjacent profile elements 32 is here preferably chosen such that the spacing b between the peak 34, or the leading edge, of a profile element 32 and the trailing edge 38 of the profile element 32 in front of it is merely of the order of magnitude of the thickness of the steel sheet used to produce the profile elements 32 and is approximately 1% to 5% of the overall extent (=spacing c between leading edge 34 and trailing edge 38) of the relevant profile element 32 in the transverse direction 22.

In addition, covering struts 42, which extend in the transverse direction 22 with regular spacings relative to one another and span over the profile elements 32, can be mounted on the outside 40 of the cover 2 and be welded to the profile elements 32 at the contact locations. The covering struts 42 are formed for example by round steel elements with a diameter of 20 mm to 30 mm.

This realizes penetration protection against projectiles that strike the cover from the outside from different flight directions and invade the intermediate spaces between the profile elements 32, as is indicated in FIG. 3 by way of trajectories 44. In addition, the free flow cross section for the air exchange between the outside 40 (exhaust-air zone) and the inside 46 of the cover 2 is kept as large as possible, while the number and the extent of direction deviations to which the passing air flow is subjected is kept comparatively small. Thus, the air exchange can be markedly effective despite the realized full-protection barrier. On account of the chosen dimensions of the individual components, it is also possible, if required, to support comparatively large static and dynamic impact and area loads.

The cover 2 can of course be used not only for ventilation openings 4 in the building complex of a nuclear-engineering plant, but also in diverse other buildings, in which the above-described properties are advantageous. 

1. A protective cover for a ventilation opening in a plant space of a nuclear-engineering plant, the protective cover comprising: a rectangular frame having a longitudinal direction and a transverse direction; and a plurality of elongate profile elements disposed in a mounting plane in said rectangular frame, said profile elements aligned in said longitudinal direction such that said profile elements are parallel to one another, and are shaped in a same way and orientated in a same way, wherein each of said profile elements having an L-shaped cross section or a V-shaped cross section with at least two limbs that meet in a peak, with said peak pointing in said transverse direction, and wherein a first spacing between said profile elements that immediately follow each other is chosen such that there is no rectilinear passage between said profile elements.
 2. The protective cover according to claim 1, wherein said two limbs of said profile elements meet in said peak at an angle that ranges from 80° to 110°.
 3. The protective cover according to claim 1, wherein, when viewed in said transverse direction, a second spacing which characterizes an overlap between a leading edge of said profile element and a trailing edge of said profile element that is located immediately in front of it is approximately 0.5% to 5% of a total width of said profile element in said transverse direction.
 4. The protective cover according to claim 1, wherein said two limbs of said profile elements have same dimensions.
 5. The protective cover according to claim 1, wherein said profile elements have a cross section being constant over an entire longitudinal extent.
 6. The protective cover according to 1, wherein each of said profile elements have two end faces, at which each of said profile elements is welded to said frame.
 7. The protective cover according to claim 1, wherein said profile elements are configured in a unipartite manner and produced by bending an originally planar steel sheet.
 8. The protective cover according to claim 1, wherein said rectangular frame is composed of said profile elements with U-shaped cross sections or double-U-shaped cross sections.
 9. The protective cover according to claim 1, wherein said two limbs of each of said profile elements meet in said peak at an angle of 90°. 